footer: Add a semi-flexible template system

internal/dis/component/control/static/custom/context.go

@@ -0,0 +1,90 @@
+package custom
+
+import (
+	"html/template"
+	"net/http"
+	"reflect"
+	"time"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
+	"github.com/FAU-CDI/wisski-distillery/pkg/httpx"
+	"github.com/gorilla/csrf"
+	"github.com/tkw1536/goprogram/lib/reflectx"
+)
+
+// baseContextName is the name of the [BaseContext] type
+var baseContextName = reflectx.TypeOf[BaseContext]().Name()
+
+// BaseContext represents a context shared by all the templates.
+//
+// This context should always be initialized using the [custom.Update], [custom.New] or [custom.NewForm] functions.
+// Other invocations might cause an error at runtime.
+type BaseContext struct {
+	inited bool // has this context been inited
+
+	GeneratedAt time.Time // time this page was generated at
+
+	CSRF template.HTML // CSRF Field
+}
+
+// constants that are used in various parts of the template to render stuff
+const (
+	errorPrefix template.HTML = `<div style="z-index:10000;position:fixed;top:0;left:0;width:100vh;height:100vw;background:red;text-align:center;padding:10vh 10vw;font-size:xx-large;font-weight:bold">`
+	errorSuffix template.HTML = "</div>"
+
+	csrfError template.HTML = errorPrefix + "CSRF used but not provided" + errorSuffix
+	initError template.HTML = errorPrefix + "BaseContext not initialized" + errorSuffix
+)
+
+// Use updates this context to use the values from the given base.
+// For convenience the passed context is also returned.
+func (tc *BaseContext) use(base component.Base, r *http.Request) *BaseContext {
+	tc.inited = true
+
+	tc.GeneratedAt = time.Now().UTC()
+
+	// setup the CSRF field
+	tc.CSRF = csrfError
+	if r != nil {
+		tc.CSRF = csrf.TemplateField(r)
+	}
+
+	return tc
+}
+
+func (bc BaseContext) DoInitCheck() template.HTML {
+	if !bc.inited {
+		return initError
+	}
+	return ""
+}
+
+// NewForm is like New, but returns a new BaseFormContext
+func (custom *Custom) NewForm(context httpx.FormContext, r *http.Request) (ctx BaseFormContext) {
+	ctx.FormContext = context
+	ctx.use(custom.Base, r)
+	return
+}
+
+// RenderContext is exactly like NewForm, but returns any to be used as httpx.Form.RenderTemplateContext
+func (custom *Custom) RenderContext(ctx httpx.FormContext, r *http.Request) any {
+	return custom.NewForm(ctx, r)
+}
+
+// Update updates an embedded BaseContext field in context.
+//
+// Assumes that context is a pointer to a struct type.
+// If this is not the case, might call panic().
+func (custom *Custom) Update(context any, r *http.Request) *BaseContext {
+	ctx := reflect.ValueOf(context).
+		Elem().FieldByName(baseContextName).Addr().
+		Interface().(*BaseContext)
+	ctx.use(custom.Base, r)
+	return ctx
+}
+
+// BaseFormContext combines BaseContext and FormContext
+type BaseFormContext struct {
+	BaseContext
+	httpx.FormContext
+}